1. Field of the Invention
The present invention relates to an electron-emitting device, and more particularly to a surface conduction electron-emitting device that emits electrons when an electric current flows in a highly resistant thin film.
2. Related Background Art
A device capable of emitting of electrons with a simple structure is the cold cathode device reported by M. I. Elinson et al (Radio Eng. Electron Phys., VOL. 10, pp.1290-1296, 1965).
This device utilizes the phenomenon that electron emission is caused by transmitting an electric current to a thin film formed with a small area on a substrate and in parallel to the surface of the film, and is generally called a surface conduction electron-emitting device.
Surface conduction electron emitting devices that has been reported includes those employing a SnO.sub.2 (Sb) thin film developed by Elinson et al., those employing an Au thin film. (G. Dittmer, "Thin Solid Films", Vol. 9, p.317, 1972), those comprising an ITO thin film, (M. Hartwell and C. G. Fonstad, "IEEE Trans. ED Conf.", p.519, 1975), and those comprising a carbon thin film [Hisaji Araki, "SHINKU" (Vacuum). Vol. 26, No. 1, p.22. 1983].
A typical device constitution of these surface conduction electron-emitting devices is shown in FIG. 17. In FIG. 17, a conventional surface conduction electron emitting device comprises an insulating substrate 5 having thereon a highly resistant thin film 4 provided between a high-potential electrode 1 and a low-potential electrode 2. A where a voltage is applied from an external electric source 3 and thereby electrons are emitted from the highly resistant thin film 4.
In these surface conduction electron-emitting devices, it has been hitherto practiced to previously form an electron-emitting region 4 (a high-resistance thin film) by an energizing heat treatment, called "forming", before effecting the electron emission. More specifically, a voltage is applied between the above electrode 1 and electrode 2 to energize the thin film formed with an electron-emitting material to bring the thin film to be locally destroyed, deformed or denatured owing to the Joule heat thereby generated, thus forming the electron-emitting region 4 (a high-resistance thin film) kept in a state of electrically high resistance to obtain an electron-emitting function.
However, such a conventional surface conduction electron-emitting device has the following disadvantages.
(1) The light-emitting region flickers.
(2) As shown in FIG. 18, the electron beam tends to deflect by the distance L toward the high-potential electrode 1 side, and in general the beam diverges.
(3) Accordingly, as shown in FIG. 19 it is necessary to externally provide a focusing lens system to effect the focusing of the electron beam. This, however, requires the preparation of external focusing lenses 17 and 18, requiring an additional step.
(4) A complicated operation is required to obtain axial alignment on the basis of electron optics between the outer focusing lenses 17 and 18 and the surface conduction electron-emitting device.